Binder and binder-based size for mineral fibers

ABSTRACT

A size for insulating type glass fibers, comprising an epoxy resin of a glycidyl ether dispersable in water, an amino setting agent having a flash point over 180° C. and, as additives, 0.1 to 2% of silane and 0 to 15% of a mineral oil, each calculated per 100 parts of dry resin.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the use of a thermosetting synthetic resin inthe production of products based on mineral fibers, in particular glassfibers such as mineral fiber mats which are employed in the manufactureof thermal insulation and/or in the soundproofing of buildings.

2. Description of the Background

Most mineral-fiber based insulating materials employ a binder for thefibers which ensures the mechanical strength of the material, i.e., itbinds the fibers together. The binder must be dispersed homogeneouslyamong the fibers in order to avoid forming bundles of fibers surroundedby lumps of binder within a group of more brittle and therefore dustierfibers. The binder is always used in a diluted state in a size.

It is known to use a thermosetting phenolic molding resin(phenol-formaldehyde) or an amino-aldehydic resins(melamine-formaldehyde or urea-formaldehyde) resin as a binder. The mostfrequently used binders are resols which are the products of thecondensation in the presence of alkaline or alkaline-earth catalysts, ofphenols, having open ortho- and para-sites, and aldehydes, primarilyformaldehyde. These resins form a size which, in addition to water,contains urea which serves to reduce the free formaldehyde content andalso acts as a binder, along with various additives such as oil,ammonia, coloring agents and, if necessary, fillers.

There are very many criteria, and of different types, involved in theselection of a binder, without forgetting however that a binder mustabove all adhere correctly to the glass.

First, it is essential that the binder be rheologically compatible withthe fiber manufacturing process. Without going into unnecessary details,the glass fibers are usually produced using a centrifuge with avertically oriented axis into which a continual jet of molten glass isintroduced. The glass is sprayed towards the peripheral wall of thecentrifuge from which it escapes in the form of filaments through amultitude of tiny orifices. The filaments produced are drawn out andpulled downwards by a high temperature high pressure gas current. Thefibers obtained are collected on a gas permeable conveyor and thus forma mat of varying thickness depending on the speed of the conveyor.

The size should ideally coat each fiber produced in this way perfectly.It is therefore preferable to spray the size compound onto the fiberswhile the fibers are still separate, i.e., before the mat is formed.Consequently, the size is sprayed into the fiber reception hood, belowthe burners which generate the gas current to draw out the fibers. As acorollary to this operation it is forbidden to use inflammable organicsolvents and/or pollutants in formulating the size, since the risk offire and/or pollution in the reception hood is too high. In addition,the resin serving as binder must not polymerize too rapidly beforetaking on the desired shape.

Furthermore, although this polymerization should not be too rapid, itshould not take too long. However, on this point, resins currently inuse are not perfectly satisfactory since complete polymerization isachieved in a time compatible with a high production rate only afterremaining in a high temperature over at approximately 250° C. which is ahigh power consumer.

Lastly, the resin and its implementation process must be of relativelymoderate cost which is compatible with that of glass fiber manufactureand must not lead either directly or indirectly to the formation oftoxic or polluting effluents. In this respect, a choice by an industrialconcern has been to select resins which do not require the use offormaldehyde in their manufacture, and which in addition do not releasesignificant quantities of formaldehyde when they decompose under theeffects of great heat. In such conditions, the product is, of course,non-toxic and in addition does not give off an unpleasant odor if itshould burn.

In an industry associated with the insulating glass fiber industry,i.e., the reinforcement glass fiber industry, it is known to sheathglass fibers with an epoxy resin. The sizing operation has the doubleobject of protecting the fibers individually so that they are thus lesssensitive to friction and offer better bonding to the plastic materialfor which the fibers act as reinforcement. But in this case, there is noattempt to link the glass fibers and nothing allowed concluding thatglass/glass bonding was sufficiently solid for good mechanicalresistance and localized throughout the total thickness.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a sizefor insulating fibers.

Another object is to provide a method by which insulating glass fibersmay be treated with a sizing agent.

Briefly, these objects and other objects of the present invention ashereinafter will become more readily apparent can be attained by asizing agent for insulating glass fibers which is an epoxy resin of aglycidyl ether dispersed in water, an amino hardening agent having aflash point over 180° C., and, as additives, 0.1 to 2% silane and 0 to15% of a mineral oil, each calculated on 100 parts of dry resin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

By being placed in an aqueous medium is meant a resin directlydispersable in water or likely to be emulsified with or without theaddition of an emulsifying agent.

Suitable epoxy resins for use in the invention have a meanpolymerization index n from 0 to 1 inclusive and preferably under 0.2, nbeing equal to the mean number of supplementary bisphenol A groups perglycidylic ether molecule obtained by condensation of epichlorhydrin##STR1## and of bisphenol A (HO--C₆ H₄ --C(CH₃)₂ --C₆ H₄ --OH), thecondensation reaction being carried out in strictly stoichiometricconditions (2 moles of epichlorhydrin per one mole of bisphenol A)giving a glycidylic ether of index n=0. Resins with a low polymerizationindex, and therefore shorter chains, usefully form a denser reticulatednetwork which one finds leads experimentally to products of highermechanical strength. However, an epoxy resin of index n=0 is notpreferred since it tends to crystallize during storage and is much moredifficult to synthesize since it is purer and thus more costly.

By non-volatile amino setting agent is meant a setting agent having aflash point over 180° C. Indeed, under these conditions, noself-igniting is observed in the fiber reception hood where the binderis sprayed.

Suitable amino hardening agents include primary, secondary, aliphatic,alicyclic, aromatic and araliphatic polyamines and polyaminoamides. TheNH equivalent molar mass, i.e., the quantity of product necessary toobtain the equivalent of one amino-hydrogen link per mole, is chosenpreferably at under 100 g which corresponds to a high number of reactivesites per molecule.

Furthermore, one can use a catalytic agent for example of the tertiaryamino type.

The polymerization index and NH equivalent molar mass are two fairlysymmetrical conditions and it is possible to compensate, at least to anextent, for a fairly poor polymerization index by using a setting agentof suitable NH equivalent molar mass and vice versa.

The hardening agents belonging to the group of polyacids and acidanhydrides are, in general, excluded from the sphere of the presentinvention, because of their very low solubility in water (a phenomenonwhich poses considerable implementation problems) and because of theircorrosive nature made worse by their high cost. Phenolic andaminoplastic resins, which release formaldehyde when baked, andhardening agents of the urea, melamine, and quanamide type, which have alow degree of solubility and entail the use of an accelerator, are alsoexcluded.

On the other hand, suitable hardening agents include those of thepolyamide and amino-polyamide type. The conditions for use of thesemoderately-priced products, which do not release formaldehyde whenbaked, are obtained with relative simplicity. However, this type ofhardening agent has the disadvantage that it produces a reaction atrelatively low temperatures, thus entailing risk of pregellation.Furthermore, some are corrosive and, when heated, release largequantities of amino compounds, thus causing a danger of pollution. Thesedisadvantages are not exhibited in hardening agents of thedicyanodiamide (DCN) type, which are inexpensive, non-toxic,non-volatile and noncorrosive, have a low degree of solubility in water,and, above all, react almost always only when heated. An impregnatedcake may be kept for nearly one year without giving evidence ofsolidification of the resin.

The resin sprayed onto the fibers must not harden before the mat isformed that is to say, prehardening of the resin should be nominal. Ithas been found that this condition is satisfied if the epoxy resinhardening time is over 25 minutes at 100° C., the gelling time being, bydefinition, the time needed at a given temperature for a certainquantity of resin to attain a viscosity set at 3000 centipoises. Withthe usual phenoplastic resins, a hardening time of 25 minutes is judgedinsufficient. Resins are preferred which have a gelling time of over 1hour which is highly limiting. With epoxy resins, much shorter hardeningtimes are possible, surprisingly, if necessary using more dilute resins.It seems, indeed, that phenoplastic epoxy resin/water systems are lessstable in the oven than phenoplastic resin/water systems which enableselimination of the water more easily.

In this invention, formaldehyde is not required to prepare the size andfurther a significant amount of formaldehyde is not driven off in theoven. In addition, complete polymerization can be carried out at atemperature under 220° C. which reduces the risk of producing pollutantproducts in the oven which require later elimination, by pyrolysis inparticular. Other characteristics of the invention are described indetail below referring to comparative tests carried out on three resinsA, B, C which satisfy the following formulations:

RESIN A Formaldehyde-phenolic resin (standard resin) Dry part: 55% (byweight) of formaldehyde resin, whose phenol/formaldehyde ratio is equalto 3.2, with mineral catalysis less than 20 mPa of viscosity at 20°C.-and 45% of urea.

RESIN B Bi-compound epoxy resin based on diglycidylether of bisphenol A(Europox 756, trademark of the SCHERRING company; epoxy index 0.54, 0.02(epoxy mole for 100 g); epoxy equivalent 178-192 (g/mole); meanpolymerization index n=0.1.

RESIN C Bi-compound epoxy resin Noxyl 865, trademark of the SAVIDcompany, epoxy index 0.33 (epoxy mole for 100 g); epoxy equivalent 300g/mole, mean polymerization index n=0.91.

HARDENING

AGENT D Water-based polyamine, Euredur 36, patented trademark of theSCHERRING company; flash point 190° C., dry extract 80%, NH equivalentmass 132 g (i.e., one NH active group for 132 g of dry product).

HARDENING

AGENT E Aliphatic polyamide XIONEL SP 3288 trademark of the SAVIDcompany; NH equivalent mass 57 g.

HARDENING

AGENT F Dicyanodiamide having a NH equivalent mass of 21 g inassociation with a polymerization accelerator, preferably of thetertiary amino type (for example tridimethylaminoethyl phenol)

Unless otherwise stipulated, the resins are mixed with the settingagents in a ratio (by weight) of one NH group for one epoxy equivalentgroup.

VISCOMETRIC BEHAVIOR

The size must have good rheological compatibility with the fibermanufacturing process. In particular, one must avoid hardening of resinoccurring in the fiber reception hood before the mat is formed in orderto avoid forming nonhomogeneous fibrous masses.

To estimate the viscosimetric behavior in a container thermostaticallycontrolled at 100° C., 10 g of resin is placed in a 30% solution inde-ionized water. A viscosimetric probe is immersed in the container andthe time taken for the viscosity to reach 3000 centipoises is measured.

Test n° 1 (resin A) : 60'

Test n° 2 (resin B+setting agent D) : 27'

Test n° 3 (resin B+setting agent F) ; 49'

The gelling times obtained during tests 2 and 3 are thus much shorterthan for test n° 1. However, one notes, surprisingly, that this has nosignificant effect, on line, on condition that the quantities of waterused are increased, if necessary.

ON LINE TEST

For the invention, the size should be sprayed onto the so-calledinsulating glass fibers, i.e., fibers obtained by an aerodynamic processof drawing out of fibers with a high pressure high temperature gascurrent, as opposed to so-called textile fibers obtained by mechanicaldrawing out of filaments produced by a spinning machine. The size isparticularly suited to fibers obtained according to the TEL process,molten glass being introduced inside the centrifuge plate revolving athigh speed from which it escapes in the form of filaments through aseries of orifices practiced on the plate wall, the filaments beingdrawn out in the form of fibers by a high speed high temperature gascurrent generated by the burners surrounding the plate. The size issprayed onto the fibers before they are collected by a reception device.The sizes are prepared by dispersion of the resin in a quantity of watercalculated to bring the proportion of dry extract to 10%, then by addinga silane. For the standard resin of the examples of the presentdisclosure 3 parts of ammonia were added to 100 parts ofphenol-formaldehyde resin in compliance with standard practice.

We initially carried out the different tests on a laboratory lineproducing glass fibers at a draw out rate of 12 kg/hour. Thecharacteristics of the fiber producing unit comply with the teachings ofFrench Patent 2 223 318 and the fibers produced thus are comparable tothose obtained industrially. In the fiber-producing hood, a size issprayed onto the fibers with 2% of resin in de-ionized water. Squareswere obtained having sides of 450 mm and a thickness of 50 mm, saidsquares having a binder content of approximately 5% afterpolymerization.

TENSILE STRENGTH

The tensile strength (or "TS" given in gf/g) is measured on test samplesin the form of rings drawn out by two interior rods in compliance withstandard ASTM C 686-71T. The results of these measurements are indicatedin TABLE I. Aging is simulated by passing the test sample through anautoclave for 30 minutes at 107° C., under autogenous water pressure.

                  TABLE I                                                         ______________________________________                                        Tests           4         5       6                                           ______________________________________                                        Resin of type   A         B       B                                           Hardening agent of type                                                                       --        D       F                                           TS after preparation                                                                          600       740     750                                         (in gf/g)                                                                     TS after aging  525       400     470                                         (in gf/g)                                                                     Percentage of binder                                                                            5%        6%       5.8%                                     in finished product                                                           ______________________________________                                    

According to the invention the mechanical strengths after aging areslightly less with resins. However, they remain satisfactory. Theinfluence of the epoxy resin polymerization index n and of the aminohardening agent NH equivalent molar mass is exemplified by the followingtests (carried out with 0.5% of silane added systematically).

The resin formulations used for tests 7 to 10 of TABLE II (TS in g/f)are as follows:

Test n° 7 : resin B+hardening agent D,

Test n° 8 : resin C+hardening agent E,

Test n° 9 : resin C+hardening agent D,

Test n° 10: resin B+hardening agent E.

                  TABLE II                                                        ______________________________________                                        Test n°                                                                             7       8         9     10                                       ______________________________________                                        TS after preparation                                                                       650     617       432   697                                      TS after aging                                                                             528     526       326   574                                      % of binder  4.6     4.65      4.3   4.0                                      ______________________________________                                    

Tests 5, 7 and 10 carried out with the resin having the smallestpolymerization index give the best results after aging. Test 8 (and alsotest 6) indicate that a setting agent whose NH equivalent molar mass ishighly associated with a resin with a high polymerization index leads toproducts initially very correct, but whose mechanical strengthsdeteriorate greatly.

The poorest results are obtained with test 9 which corresponds to anepoxy resin having a high polymerization index and a hardening agentwith a high NH equivalent molar mass.

The product preferred for the invention (test 10) exhibits excellentbehavior after preparation and after aging. In addition, an adequatequantity of silane enables optimization of the properties as shown inTests 11 to 14 in TABLE III established by varying the quantity ofsilane in the different samples prepared from a type B resin and asetting agent type D.

                  TABLE III                                                       ______________________________________                                                Silane  Binder     TS after                                                                              TS after                                   Test    %       %          preparation                                                                           autoclave                                  ______________________________________                                        11      0       6.6        707     258                                        12      0.5     5.6        724     392                                        13      1.0     5.8        692     395                                        14      1.5     6.5        712     422                                        ______________________________________                                    

The main effect of adding silane is the improvement of product aging,whereas at a nearby binder rate the tensile strength (given here ingf/g) measured immediately after product preparation is practicallyconstant. The best results are obtained for a percentage of silanebetween 0.5 and 1% inclusive. In the case of insulating fiber materials,it therefore appears that the silane acts essentially by forbidding theinsertion of water molecules between the glass and the resin and not asa promoter of glass/resin bonding.

With regard to the influence of the ratio of epoxy resin to itshardening agent, a type B resin and type D hardening agent, were used towhich was added 0.5% of silane in compliance with experience gained fromthe previous tests. The results are summarized in Table IV below.

                  TABLE IV                                                        ______________________________________                                                        Hardening                                                     Test  Resin B   agent D   Binder       TS auto-                               n°                                                                           %         %         %      TS    clave                                  ______________________________________                                        15    45        55        6.2    653   336                                    16    53        47        6.3    741   400                                    17    58        42        5.4    723   346                                    18    63        37        6.2    686   388                                    19    70        30        5.2    653   316                                    ______________________________________                                    

The best results (for an identical binder rate) are obtained when theratio of the number of epoxy resin groups to the number of setting agentNH equivalent groups is close to the stoichiometric ratio, i.e., 53/43by mass for the resins of tests 15 to 19.

These first results were then checked by preparing 9 samples includingtwo reference samples based on a standard resin. These samples wereobtained on a pilot production line under conditions very close toindustrial conditions. In this line, the glass fibers are preparedaccording to the so-called "TEL" process as explained in EP patent91,866. Production of drawn-out glass is 20 tons per day. The sizes aredelivered by a dosing pump with a quantity of de-ionized water enablingthe proportion of dry extract to be brought to 10%. A silane wasemployed as an additive and an anti-dusting agent and a softener, from 0to 10% of mineral oil. One can also use other types of oil such aslinseed oil, soybean oil, safflower oil fatty acid, fish oil or Chinesewood oil or a non-drying oil such as coconut oil, palm oil or stearicacid. The sizes are sprayed into the fiber collection hood at an airpressure of 1.5 bar. A certain quantity of excess water, referred to asan overspray, is sprayed onto the fiber collection at the same time tobring the proportion of dry extract in relation to the final quantity ofwater to a value of between 5 to 8% inclusive and preferably between 6.5and 7.5%. In compliance with the data obtained from viscosimetricmeasurements, tests with the resin according to the invention werecarried out with a quantity of excess water of more than 50% more thanthat used for a standard size.

Polymerization is carried out in a ventilated oven in which the glassfiber mat penetrates between two squeeze rollers which impose upon it agiven thickness, greater than rated thickness, i.e., the minimumthickness guaranteed to the user.

Here below details are given of the preparative conditions of thedifferent samples, the rate of binder measured after polymerization anddimensional characteristics (gms substance, density, actual productthickness).

Sample n° 20

Size formulation:

phenol/formaldehyde control resin

    ______________________________________                                        type A                100    parts                                            % of silane           1      part                                             % of oil              10     parts                                            % of liquid ammonia   3      parts                                            ______________________________________                                    

Flow rate:

size (kg/h) :540

overspray (kg/h): 200

Temperature of product in oven:250° C.

Percentage of binder in finished product:5.04

Gsm substance (g/m²):878

Density (kg/m³):10.97

Thickness (mm):129.2

Sample n° 21

Size formulation:

Resin B, hardening agent D in the ratio:55/45

% of silane 0.5

Flow rate:

size (kg/h):640

overspray (kg/h):300

Temperature of product in oven:250° C.

Percentage of binder in finished product:5.88

Gsm substance (g/hu2):899

Density (kg/m³):11.24

Thickness (mm):129.3

Sample n° 22

Size formulation:

Resin B, hardening agent D in the ratio:55/45

% of silane: 0.5

Flow rate:

size (kg/h):840

overspray (kg/h):300

Temperature of product in oven:250° C.

Percentage of binder in finished product:5.06

Gsm substance (g/m²):892

Density (kg/m³):11.15

Thickness (mm):128.7

Sample n° 23

Size formulation:

Resin B, hardening agent D in the ratio:55/45

% of silane: 0.5

Flow rate:

size (kg/h):840

overspray (kg/h):300

Temperature of product in oven:250° C.

Percentage of binder in finished product:5.12

Gsm substance (g/m²):897

Density (kg/m³):11.21

Thickness (mm):129.6

Sample n° 24

Size formulation:

phenol-formaldehyde control resin

type A:100 parts

% of silane: 1 part

% of oil: 10 parts

% of liquid ammonia: 3 parts

Flow rate:

size (kg/h):540

overspray (kg/h):200

Temperature of product in oven:218° C.

Percentage of binder in finished product:4.5

Gsm substance (g/m2):916

Density (kg/m3):11.4

Thickness (mm):129.5

Sample n° 25

Size formulation:

Resin B, hardening agent D in the ratio:55/45

% of silane:0.5

Flow rate:

size (kg/h):840

overspray (kg/h):300

Temperature of product in oven: 216° C.

Percentage of binder in finished product:5.8

Gsm substance (kg/m2):916

Density (kg/m3):12.0

Thickness (mm):129.1

Sample n° 26

Size formulation:

Resin B, hardening agent D in the ratio:55/45

% of silane 0.5

% of oil 9.5

Flow rate:

size (kg/h):840

overspray (kg/h):300

Temperature of product in oven:218° C.

Percentage of binder in finished product:6.5

Gsm substance (g/m2):908

Density (kg/m3):11.3

Thickness (mm):128.2

Sample n° 27

Size formulation:

Resin B, hardening agent D in the ratio:55/45

% of silane 0.5

% of oil 9.5

Flow rate:

size (kg/h):840

overspray (kg/h):300

Temperature of product in oven:200° C.

Percentage of binder in finished product:6.2

Gsm substance (g/m2):898

Density (kg/m3):11.2

Thickness (mm):129.0

Sample n° 28

Size formulation:

Resin B, hardening agent D in the ratio : 50/50

% of silane 0.5

% of oil 9.5

Flow rate:

size (kg/h) : 840

overspray (kg/h) : 300

Temperature of product in oven : 193° C.

Percentage of binder in finished product : 6.0

Gsm substance (g/m2) : 911

Density (kg/m³): 11.4

Thickness (mm) : 131.3

Sample no. 29

Size formulation:

Resin C, hardening agent E in the ratio : 84/16

% of silane 0.5

Flow rate:

size (kg/h) : 840

overspray (kg/h) : 300

Temperature of product in oven : 240° C.

Percentage of binder in finished product : 5.95

Gsm substance (g/m²) : 920

Density (kg/m³) : 11.5

Thickness (mm) : 127.9

Sample no. 30

Size formulation:

Resin C, hardening agent E in the ratio : 84/16

% of silane : 0.5

Flow rate:

size (kg/h):740

overspray (kg/h) : 200

Temperature of product in oven : 240° C.

Percentage of binder in finished product:6.15

Gsm substance (g/m²): 899

Density (kg/m³) : 11.23

Thickness (mm) : 127.5

The size of the present invention, therefore, enables the preparation ofproducts which hardly differ from standard products from the point ofview of their dimensional characteristics (density and thickness) andthis without important modification of the manufacturing process.

Samples 20 and 24 obtained with a standard size are yellow in theabsence of specific coloring additives. Samples 21, 22 and 23 are veryslightly brown. However, samples 25 to 28 are of white color. It istherefore advantageous to maintain the temperature of the product in theoven at approximately 220° C., which enables a good polymerization ofthe binder. In addition, the final color of the product can be chosenexactly as discussed. Further, there is a diminished risk of evolvingpollutants if the oven temperature is low.

For its packaging, on removal from the oven, the product is compressedat a compression rate equal by definition to the ratio of ratedthickness to thickness under compression. The samples were tested forcompression rates equal to 4 or 6. To evaluate the dimensionalresistance of a sample, the thickness after unwrapping, calculated as apercentage of rated thickness, is indicated. This percentage, referredto as thickness recovery, can therefore sometimes exceed 100.

Thickness recovery 24 hours after manufacture for a compression rate of6 (and 4, respectively)

Sample no. 21:125.8 (133.9)

Sample no. 22:126.0 (135.1)

Sample no. 23:104.7 (119.7)

Sample no. 24:143.1

Sample no. 25:127.5

Sample no. 26:129.4

Sample no. 27:129.2

Sample no. 28:131.7

Sample no. 29:141.8 (137.2)

Sample no. 30:143.7 (136.4)

Thickness recovery 12 days after manufacture for a compression rate of 6(and 4, respectively)

Sample no. 20:135.8 (140.7)

Sample no. 21:110.7 (124.6)

Sample no. 23:113.3 (122.7)

Sample no. 23:105.3 (106.6)

Sample no. 29:137.0 (133.6)

Sample no. 30:143.7 (132.5)

The mechanical strength of the products was then tested immediatelyafter preparation of the samples, after 24 hours and then 12 days later,lastly, an artificial aging test was also conducted in the autoclave(Table V).

                  TABLE V                                                         ______________________________________                                                Tensile Strength (in gf/g) after                                      No.     preparation                                                                             24 hours   12 days                                                                             autoclave                                  ______________________________________                                        20      292                  257   177                                        21      293       279        251   146                                        22      273       281        266   210                                        23      295                  272   241                                        24      284       264              174                                        25      257       260              186                                        26      248       248              222                                        27      253       241              165                                        28      268       262              197                                        29      269       232        217   207                                        30      264       247        232   185                                        ______________________________________                                    

The products of the present invention have, after preparation, a tensilestrength close to that of standard products, however they are slightlybetter.

These tests demonstrate the possibility of producing glass fiberproducts intended in particular for thermal insulation and/or thesoundproofing of buildings, particularly light products, replacingstandard size with the size according to the invention, and this withoutmodification of the glass fiber production line operating parameters,except as regards the temperature of the oven whose hardening point isreduced by about 30 to 50° C., which saves energy.

These additional tests were undertaken, so as to verify the feasibilityof a glue containing an F-type (dicyanodiamide) hardening agent, towhich an accelerator of the 2, 4, 6 tri(dimethylaminomethyl) phenol typeis joined. This product is marketed under the trademark DMP-30 by ROHMand HAAS FRANCE, (French companies).

These three tests were run on the industrial line previously described(drawn from 20-ton glass per day, without overspray). The following glueformulations were used:

    ______________________________________                                        SAMPLE NO. 31                                                                 Glue formulation:                                                             ______________________________________                                        * control Type A resin 100    parts                                           * silane               0.3    part                                            * oil                  9.5    parts                                           * liquid ammonia       6      parts                                           * ammonium sulfate     3      parts                                           ______________________________________                                    

    ______________________________________                                        SAMPLE NO. 32                                                                 Glue formulation:                                                             ______________________________________                                        * resin B              72    parts                                            * hardening agent E    28    parts                                            * silane               0.5   part                                             * oil                  12    parts                                            ______________________________________                                    

    ______________________________________                                        SAMPLE NO. 33                                                                 Glue formulation:                                                             ______________________________________                                        * resin B              88    parts                                            * hardening agent F    12    parts                                            * accelerator          1.2   part                                             * silane               0.5   part                                             * oil                  12    parts                                            ______________________________________                                    

    ______________________________________                                                         Grams per                                                    Trial Micronaire square meter                                                                             Density Thickness                                 ______________________________________                                        31    3.35       896        11.2    125.6                                     32    3.50       899        11.2    128.1                                     33    3.60       927        11.6    158.5                                     ______________________________________                                    

    ______________________________________                                        Tensile Strength (in gf/g)/                                                   Recovery of thickness (in %)                                                  Trial   24 hours 12 days    30 days                                                                              90 days                                    ______________________________________                                        31      300/141.8                                                                              272/137.5  282/138.1                                                                            227/130.8                                  32      218/140.7                                                                              224/136.4  238/137.0                                                                            260/131.3                                  33      232/141.2                                                                              223/140.1  248/138.5                                                                            217/137.0                                  ______________________________________                                    

The DCN-based hardening agent is satisfactory from all points of view.Recovery of thickness is, in fact, equal to that observed for thestandard product after manufacture and is even better after aging.Tensile strength is, on the other hand, somewhat weaker after aging, butremains nevertheless at a high value. It should be noted, furthermore,that, when comparing tests 32 and 33, hardening agents E and F producevery similar results, but at a cost price divided by two for gluescontaining hardening agent F, which is, in fact, unquestionably thepreferred product according to the invention.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. In a size for the preparation of insulatingglass mats consisting essentially of an epoxy resin, an amino hardeningagent and, as additives, 0.1 to 20% of silane, 0 to 15% of a mineraloil, the improvement wherein said epoxy resin is a condensation productof epichlorohydrin and bisphenol A having a polymerization index n ofless than 1 and the equivalent molar mass of the hardening agent is lessthan 100 g.
 2. The size according to claim 1, wherein saidpolymerization index is less than 0.2.
 3. The size according to claim 1,wherein the polymerization index n is greater than
 0. 4. The sizeaccording to claim 1, wherein the hardening agent is added to the epoxyresin at a ratio of the number of epoxy resin groups to the number ofhardening agent NH equivalent groups virtually identical to thestoichiometric ratio.
 5. The size according to claim 1, wherein theresin hardening agent couple presents a hardening time exceeding 25minutes.
 6. The size according to claim 1, wherein the hardening agentis dicyanodiamide.